When the electrical characteristic of a semiconductor device which is an object to be measured is evaluated, it is important to precisely measure the temperature of the semiconductor device under evaluation. Particularly regarding evaluation of a temperature characteristic, unstable measurement of the temperature of the semiconductor device under evaluation results in an error in the temperature characteristic itself. Moreover, when the electrical characteristic is evaluated in order to address the requirement to apply large current/high voltage, the temperature of the semiconductor device may vary due to the application of large current/high voltage. In this case, it is also important to measure the temperature variation of the semiconductor device together with the electrical characteristic.
Under such circumstances, contact-type and non-contact type methods are known as methods for measuring the temperature of a semiconductor device. For example, in the case of the contact-type method, a thermocouple is placed in direct contact with the surface of the semiconductor device to measure the surface temperature of the semiconductor device. This method, however, is accompanied by movement of heat due to the contact and therefore does not accurately measure the temperature of the semiconductor device itself. In the case of the non-contact type method, an optical radiation thermometer may be used to measure the temperature. However, when the surface of the semiconductor device is a mirror surface, the temperature is difficult to measure. Even when the temperature can be measured, the detected temperature is easily variable depending on the setting of the emittance. Therefore, this type of method does not accurately measure the temperature of the semiconductor device.
A method for evaluating the temperature of an object to be measured is disclosed for example in Japanese Patent Laying-Open No. 2010-26715 (see PTD 1) and Japanese Patent Laying-Open No. 2013-254873 (see PTD 2).
According to Japanese Patent Laying-Open No. 2010-26715, a temperature sensor is placed on a resin table on which an object to be measured is to be mounted, and the temperature in a bath is controlled based on the temperature measured by this temperature sensor. According to Japanese Patent Laying-Open No. 2013-254873, a thermistor with leads is placed in a power module and this thermistor is used to measure the temperature of a semiconductor device.